Each home appliance signals a message, such as reception of a mail, arrival of a guest, or end of automatic washing. Each appliance, as a signal source (such as a mobile terminal device, an interphone, or a washing machine), signals a message by outputting a sound, such as a voice, a melody, or a buzzer sound.
For example, Patent Document 1 discloses a washing machine which includes a door that closes an opening through which clothes are thrown, and a door locking device with a self-maintenance function of locking the door to keep the door in a closed state. The washing machine is characterized by performing an operation termination procedure including locking the door by the door locking device. It is disclosed that the washing machine signals a warning to close the door when the door is not closed at the time of performing the operation termination procedure including locking the door.